Some Factors Affecting Release Rate of Dibromotetrachloroethane as a Fungistat for Stored Table Grapes

¹ University of California, Davis
² Central Research Division, Crown Zellerbach Corporation, Camas, Washington
³ Department of Agricultural Engineering, University of California, Davis.

Decay caused by Botrytis cinerea Pers. was most effectively controlled in stored grapes with dibromotetrachloroethane-impregnated pads if: the fruit was packed in unvented plastic-wax-coated telescope containers; each pad, 11 x 16 inches, contained 5 grams of DBTCE enmeshed between two layers of plain kraft paper; pads were packed one immediately above and one immediately below the fruit; and the grapes were stored at 31°F. 'Thompson Seedless' grapes after 3 months and 'Emperor' after 5 months had about twice as much decay as SO₂-fumigafet control fruit packed in vented containers—still very effective decay control for DBTCE, considering the length of the storage periods and large amount of inoculum placed in the packs. During storage 0.75 to 1.37 grams of DBTCE vaporized from each pad. Loss was related directly to storage temperature, initial DBTCE dose in the pad and to length of storage period. Over half of the loss occurred during the first month—probably most of this during the first 1-2 days while the fruit was cooling. The high initial concentration of DBTCE vapor had a strong fungistatic effect that persisted for several weeks, resulting in decay control nearly equal to that with SO₂ for storage periods as long as a month. Infected berries were more of a hazard in unvented than vented containers as the fungus had more tendency to spread to adjacent berries through the stems in the moist environment of the unvented pack. Stems of DBTCE-treated grapes tended to darken more than those of SO₂- treated fruit; however, they remained much more plump and attractive because of less water loss from the closed container. Likewise, the berries remained more crisp and bright, because of less shrinkage and no bleaching injury. Also DBTCE imparted no discernable odors or flavors to the fruit.